1. Field of the Invention
The present invention relates to a signaling transport converter and/or to a system and/or method of transmitting data in a communication network between a signaling entity and a peer signaling entity through a transport layer by using such a signaling transport converter.
2. Related Prior Art
In the last years, the implementation and usage of data and telecommunication networks, i.e. of wire based networks, such as, for example, the Integrated Services Digital Network (ISDN), or wireless networks, such as, for example, the cdma2000 (code division multiple access) system, cellular 3rd generation communication networks, the Universal Mobile Telecommunications System (UMTS), the General Packet Radio System (GPRS), the Wireless Local Area Network (WLAN), increased all over the world. Various organizations, such as the ITU-T (International Telecommunication Union—Telecommunications), the 3rd Generation Partnership Project (3GPP), 3rd Generation Partnership Project 2 (3GPP2), Internet Engineering Task Force (IETF), and the like are working on standardization for such networks.
In general, the system structure of a communication network is such that a user equipment, such as a mobile station, a mobile phone, a fixed phone, a personal computer (PC), a laptop, a personal digital assistant (PDA) or the like, is connected via transceivers and interfaces, such as an air interface, a wired interface or the like, to an access network subsystem. The access network subsystem controlling the communication connection to and from the user equipment comprises components such as Base Transceiver Stations (BTS), Radio Network Controllers (RNC) and the like which are connected via an interface to a corresponding core or backbone network subsystem. The core (or backbone) network subsystem switches the data transmitted via the communication connection to a destination, such as another user equipment, a service provider (server/proxy), or another communication network. The core network subsystem may be connected to a plurality of access network subsystems. The respective network structure may vary, as known for those skilled in the art and defined in respective specifications, for example, for UMTS, GSM and the like.
Generally, for properly establishing and handling a communication connection between network elements such as the user equipment and another user terminal, a database, a server, etc., one or more intermediate network elements such as support nodes or service nodes are involved. Data, such as voice, multimedia, control signaling data and the like, are transmitted, for example, by means of a packet based data transmission. One example for a utilized packet based data transmission protocol is the Internet Protocol (IP).
An indispensible requirement for such telecommunication networks is a reliable transport of the control signaling between network elements. However, due to the fact that different types of transport protocols may be used, and due to the stack-like structure of the utilized protocols, the signaling transport between network entities requires special means and/or services provided in the nework structure.
One type of solution for providing a signaling transport service for signaling entities in a communication network is specified by the standardisation body ITU-T in the form of a so-called Signaling Transport Converter (STC). The STC is specified in the series ITU-T Q.2150.x, specifically in ITU-T Recommendation Q.2150.0 “Generic Signalling Transport Service”, ITU-T Recommendation Q.2150.1 “Signalling Transport Converter on MTP3 and MTP3b” (MTP: Message Transfer Part), ITU-T Recommendation Q.2150.2 “Signalling Transport Converter on SSCOP (Service Specific Connection Oriented Protocol) and SSCOPME (Service Specific Connection Oriented Protocol Multilink or Connectionless Environment)”, and ITU-T Recommendation Q.2150.3 “Signalling Transport Converter on SCTP (Stream Control Transmission Protocol)”.
In general, the STC is used to exchange ATM (Asynchronous Transfer Mode) signaling messages with peer signaling entities and to receive information about the conditions of the signaling network. The introduction of the STC in the telecommunication network structure makes the transport layer independent of the application layer by means of which the reliability of the transport link for data transmission is increased. In other words, the concept of STC makes a signaling application independent of its transport layers. One major benefit of this concept of STC is that a change of the transport protocol used for the signaling transport does not require a modification of the signaling application itself.
According to the ITU-T standard, all variants of STC provide the same services to the signaling application by a well-defined interface. In FIG. 7, an exemplary overview of the existing STC standards and the underlying transport protocols according to the ITU-T Recommendations is shown (FIG. 7 is based on an excerpt from ITU-T Q.2150.0 “Example protocol stacks for the Generic Signalling Transport Service” (FIG. 5-2/Q.2150.0)).
In detail, reference signs 101 to 105 denote the respective transport layers defined by the respective protocols. Additionally, the respective specifications or sources of the protocols is given, i.e. ITU-T Recommendations Q.704 and Q.2210 for MTP3 and MTP3b, respectively, ITU-T Recommendations Q.2110 and Q.2111 for SSCOP and SSCOPMCE, respectively, and IETF Request for Comments (RFC) 2960 for SCTP. Reference signs 106 to 108 denote the STCs defined by the ITU-T Recommendations Q.2150.x mentioned above which are linked to their respective transport layer(s) by means of commonly known interfaces. Via these interfaces, information elements or primitives are transmitted between the STCs and the transport layers which are described, for example, in the ITU-T Q.2150.x and thus not explained in detail at this point. On the other hand, the STCs 106 to 108 are linked to respective signaling entities (not shown in FIG. 7) via another interface. Over this interface, also information elements or primitives are transmitted to and from the STCs. For the connection between the STC and the signaling entity, a Generic Signaling Transport service according to ITU-T Q.2150.0 is used by means of which the idiosyncrasy of the underlying signaling transport mechanism must not be considered by the signaling application.
However, there may be a problem concerning the compatibility of the existing STC concepts to recent or future implementations of network elements. For example, in case of a BTS which is internally based on an IP architecture between the transport and baseband part, the implementation of the existing STC solutions may be problematic or they are even not applicable. According to the structure of such BTS, the Transport part connects the standard Iub/ATM interface to the internal IP architecture. For the control of the IP streams for the user traffic at point-to-point connections, an inter-node protocol and nodal functions are required, which may be based, for example, on an IP connection control signaling defined by ITU-T Recommendation Q.2631.1 “IP connection control signalling protocol Capability Set 1”. Such an IP connection control signaling is in particular selected to control the IP streams for the user traffic with respect to the Open BTS Architecture Initiative (OBSAI), which specifies vendor independent interfaces between BTS modules.
Currently, according to ITU-T, when an IP transport is used in the architecture of a BTS, for example, the IP connection control signaling uses services provided by the “STC on Stream Control Transmission Protocol (SCTP)” according to ITU-T Recommendation Q.2150.3. According to RFC 2960 “Stream Control Transmission Protocol”, the SCTP is “designed to transport PSTN signaling messages over IP networks, but is capable of broader applications. SCTP is a reliable transport protocol operating on top of a connectionless packet network such as IP. It offers the following services to its users:                acknowledged error-free non-duplicated transfer of user data,        data fragmentation to conform to discovered path MTU size,        sequenced delivery of user messages within multiple streams, with an option for order-of-arrival delivery of individual user messages,        optional bundling of multiple user messages into a single SCTP packet, and        network-level fault tolerance through supporting of multi-homing at either or both ends of an association.        
The design of SCTP includes appropriate congestion avoidance behavior and resistance to flooding and masquerade attacks.”
Thus, when applying SCTP in the interface between the transport and baseband part of a BTS, in particular in case of a BTS being internally based on an IP architecture between the transport and baseband part, there may arise a problem in that SCTP is not optimized with respect to such network components as SCTP provides many not needed services which in turn consume a lot of resources. Furthermore, SCTP components may show some difficulties with respect to reliability and availability as SCTP has been specified in October 2000, and updated in September 2002, which may lead to unwanted problems in the implementation phase due to not yet discovered compatibility problems. In other words, the maturity and availability of SCTP is not ensured.